America's most unequal cities

And the most unequal city in America is… Atlanta! Where the rich earn nearly 19 times the poor.

A new study from the Brookings Institute analyzed data from the U.S. Census Bureau and ranked America's 50 largest cities. It compared the household income of the richest in each city -- defined as the 95%th percentile -- with that of the poorest, or the bottom 20% of households.

But the reason Atlanta is so unequal isn't because the rich are so rich there. It's because the poor are so poor. The cutoff for the bottom 20% is just $14,850 a year. Nationwide, a household would have to make $20,968 to cross the 20th percentile.

San Francisco is the second most unequal city, where the rich earn nearly 17 times the poor. There, the top 5% of households earn at least $353,576 a year. Thanks, Silicon Valley.

Other interesting finds: Cities are generally more unequal than the rest of the country. Which makes sense, given that they are often home to the highest-paying jobs, but also tend to offer social services and public transit that attract lower income folks.

Using similar logic, the most egalitarian cities tend to be newer ones with major sprawl -- places that aren't necessarily magnets for corporate headquarters but also places where having a car (and the money to afford one) is essential.

The study also noted that urban inequality hasn't risen that much in most places over the last 10 years.

That could be because the recession hit both rich and poor people alike. Incomes have recovered for the rich recently, but the study's timing may not have captured that, said Alan Berube, a senior fellow at Brookings' Metropolitan Policy Project.

Also, gentrification in places like New York, San Francisco and Seattle is playing a role -- with more poor people being pushed into the suburbs or elsewhere.

"There are just fewer of the very poor living in some urban centers today," said Berube.

Steve Hargreaves is a senior writer covering economic, energy and environmental issues at CNNMoney. Previously, he worked out of Istanbul and Bangkok, and has been published in the Village Voice and the Australian Financial Review. He tweets at @HargreavesCNN